Illative (abbreviatedILL; from Latin illatus "brought in") is, in the Finnish language, the Estonian language, the Lithuanian language, and the Hungarian language, the third of the locativecases with the basic meaning of "into (the inside of)". An example from Hungarian is "a házba" (into the house, with "a ház" meaning "the house"). An example from Estonian is "majasse" and "majja" (into the house), formed from "maja" (a house). An example from Finnish is "taloon" (into the house), formed from "talo" (a house). An example from Lithuanian is "laivan" (into the boat) formed from "laivas" (boat).

The case is formed by adding -hVn, where 'V' represents the last vowel, and then removing the 'h' if a simple long vowel would result. For example, talo + Vn becomes taloon with a simple long 'oo'; cf. maa + hVn becomes maahan, without the elision of 'h'. This unusually complex way of adding a suffix can be explained by its reconstructed origin: a voiced palatal fricative. (Modern Finnish has lost palatalization and fricatives other than 'h' or 's'.) In the dialect of Pohjanmaa, the 'h' is not removed; one says talohon.

The illative case, denoting direction of movement, is now less common in the standard language but is common in the spoken language, especially in certain dialects. Its singular form, heard more often than the plural, appears in books, newspapers, etc. Most Lithuanian nouns can take the illative ending, indicating that from the descriptive point of view the illative still can be treated as a case in Lithuanian. Since the beginning of the 20th century it isn't included in the lists of standard Lithuanian cases in most grammar books and textbooks, and the prepositional construction į+accusative is more frequently used today to denote direction. The illative case was used extensively in older Lithuanian; the first Lithuanian grammar book, by Daniel Klein, mentions both illative and į+accusative but calls the usage of the illative "more elegant". Later, it has often appeared in the written texts of the authors who grew up in Dzukija or Eastern Aukštaitija, such as Vincas Krėvė-Mickevičius.

The illative case in Lithuanian has its own endings, which are different for each declension paradigm, although quite regular, compared with some other Lithuanian cases. An ending of the illative always ends with n in the singular, and sna is the final part of an ending of the illative in the plural.